* Causes of train derailment still under investigation

JOHANNESBURG, July 24 (Reuters) - South Africa’s logistics group Transnet [TRAN.UL] has shut down its iron ore rail line after a train carrying ore was derailed, the company said on Saturday, threatening to slow exports of the raw material.

Transnet’s freight arm’s spokesman, Sandile Simelani, said it would take some time to clear the line between Kumba Iron Ore’s (KIOJ.J) Sishen mine and the port of Saldhana following the derailment.

Kumba, a unit of global miner Anglo American (AAL.L) and the world’s 10th-largest iron ore producer, uses the line to export the steel-making ingredient to overseas markets.

Simelani said the cause of the derailment of the train, which had 124 wagons carrying the raw material, had not yet been established but workers were busy clearing the site.

"We will need to conduct an enquiry to establish what happened. We will also need to clear the iron ore (from the rail track) before the line can be opened, but I can’t tell when this is going to happen," Simelani told Reuters.

Transnet said exports of iron ore in the 2010 financial year rose to 44.7 million tonnes, in line with customer commitments, compared with 36.8 million tonnes in the previous financial year. (来源：Reuters)